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Sedimentation equilibria in polydisperse ferrofluids: critical comparisons between experiment, theory, and computer
Ekaterina A Elfimova1, Alexey O Ivanov, Ekaterina V Lakhtina
1Institute of Mathematics and Computer Sciences, Ural Federal University, 51 Lenin Avenue, Ekaterinburg 620000, Russia.
Soft Matter
|April 5, 2016
Summary
This study develops a theory for particle concentration in ferrofluids, validated by simulations and experiments. The theory accurately predicts behavior in monodisperse systems and, with polydispersity, matches real ferrofluid experiments.
Area of Science:
- Physics
- Materials Science
- Physical Chemistry
Background:
- Ferrofluids exhibit complex particle behavior due to magnetic dipole interactions.
- Understanding particle concentration profiles is crucial for predicting ferrofluid properties.
Purpose of the Study:
- To develop and validate a theoretical model for particle concentration equilibrium in dipolar fluids.
- To compare theoretical predictions with simulation and experimental data for monodisperse and bidisperse systems.
Main Methods:
- Development of a theory based on local-density approximation and logarithmic free energy.
- Monte Carlo simulations of monodisperse and bidisperse dipolar hard-sphere fluids.
- Experimental analysis of magnetic susceptibility profiles in a real ferrofluid.
Main Results:
- The theory accurately predicts particle concentration in monodisperse dipolar hard-sphere fluids.
- The model shows excellent agreement at low volume fractions for bidisperse systems.
- Experimental ferrofluid data aligns with the theory when polydispersity (binary mixture) is considered.
Conclusions:
- The developed theory provides a robust framework for understanding ferrofluid sedimentation.
- Polydispersity significantly impacts particle concentration profiles in real ferrofluids.
- The study successfully reconciles theoretical models with experimental observations.
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